[LyX/master] Set buffer correctly when deleting column in math grid

[Jean-Marc Lasgouttes]

commit 5915d69eaf66cf89d5c5f24f436bc44afca24dfb
Author: Jean-Marc Lasgouttes <lasgout...@lyx.org>
Date:   Wed Aug 28 18:21:17 2019 +0200

    Set buffer correctly when deleting column in math grid
    
    This is a followup to 837bcbb0.
    
    Fixes bug #11623.
---
 src/mathed/InsetMathGrid.cpp |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/src/mathed/InsetMathGrid.cpp b/src/mathed/InsetMathGrid.cpp
index fe823d4..910450d 100644
--- a/src/mathed/InsetMathGrid.cpp
+++ b/src/mathed/InsetMathGrid.cpp
@@ -896,6 +896,8 @@ void InsetMathGrid::delCol(col_type col)
                        tmpcellinfo.push_back(cellinfo_[i]);
                }
        swap(cells_, tmpcells);
+       // copying cells loses the buffer reference
+       setBuffer(*buffer_);
        swap(cellinfo_, tmpcellinfo);
 
        colinfo_.erase(colinfo_.begin() + col);